1. Field of the Invention
The present invention relates generally to the field of optical networks, and particularly to gain control in an optical amplifier.
2. Description of Related Art
Optical amplifier is a major network element for dense wavelength division multiplexer (DWDM) optical networks. It boosts the optical signal power without the need to convert all DWDM channels back to electrical domain and back to optical domain. As development unfolds, optical nodes are emerging as the building block for optical networks. Optical nodes amplify, perform dispersion management, monitor optical performance, and manipulate wavelengths, such as an optical add drop multiplexer (OADM) and/or an optical cross connect (OXC), in optical domain. Optical amplifiers operates as building blocks in constructing an optical node. As DWDM networking progresses, more intelligent optical amplifiers are needed so that cost-effective, fully scalable, and automatic provisional services can be delivered.
Conventional optical amplifiers operate in constant output power with automatic level control (ALC) loop, and/or constant gain with automatic gain control (AGC) loop. When an amplifier operates in AGC mode, it compares its input and output power and control the pump laser power so that the amplifier gain, i.e. the ratio between output and input, is constant. AGC is commonly required for DWDM system amplifiers, since it ensures that each DWDM channel receives same amount of gain from optical amplifier irrespective to the number of input channels into the amplifier. A shortcoming of this approach is that the AGC is limited to amplifier""s own input and output. As DWDM network node evolves, more than one optical amplifiers are needed for one network node. And AGC needs to be configured across all amplifiers in one node. Accordingly, the present invention addresses these needs.
The invention provides a reconfigurable AGC loop design for an optical amplifier with a software provisional switch in the AGC loop inside the optical amplifier. On the input side, there is a 1xc3x97m switch for switching a first input to the input of an optical amplifier, or to route other external pins to the optical amplifier. On the output side, there is a 1xc3x97n switch for switching a first output to the output of an optical amplifier, or to route other external pins to the optical amplifier. The AGC loop inside an optical amplifier is available to operate with other external signals. This reconfigurability unleashes the AGC loop capability that is traditionally confined to individual optical amplifier.
Advantageously, the present invention provides a greater flexibility in the operation of an optical node for interfacing with external pins. The present invention further advantageously simplifies the design of an optical node significantly.
Other structures and methods are disclosed in the detailed description below. This summary does not purport to define the invention. The invention is defined by the claims